Icom: IC-7100 power drain when pushing PTT

Hello folks,

My father who's been a HAM radio amateur for many decades (but doesn't speak english) asked me to ask something here. He recently bought an ICOM IC-7100 which is great but every time he press the PTT without talking, he notices a drain of 3 ~ 4 AMPS.

He sold his old YAESU transeiver so new he can't compare but he thinks it didn't drain power until he began to talk.

I've looked if maybe there's a sub-tome being transmitted but there's no option for that in SSB (only in FM) and we're talking about 40 mts LSB here.

I also thought about the possibility of it being the carrier signal (without the modulation as he is not speaking yet) that draws the power. Could it be?

Thanks in advance!

PS: About totake my exam so some time next year I hope I ask stuff here as a HAM operator

I've got a 7100 but I don't have a metered DC supply on it.... so I couldn't tell you if that is normal or not. So I think we need some more info, and answering these questions may help -
1) What make, model, and current rating / capacity power supply is being used with the IC-7100?
2) Does the power supply have a meter, and is that how he is noticing the 3-4 amp drain?
3) Why is this of concern (and there may be reasons, e.g. solar powered, battery drain / recharge, etc.)?

I sold my 7100 but as I recall that sounds about right. Radio is going from receive with the PA "off" to biased on in preparation to transmit. I would expect idle "on" current in the 3-4 range and to ramp up as you speak with peaks to near 20 if power set to 100%.

popnokick:

1) Don't know... is chinese. 30 AMP (very well tested and works like a charm without noise)
2) yup... as seen in attachment
3) No concern... just curoius to know if it's normal or not

mcscanner:

That sounds both right and logic. You say it might be either the carrier signal or the "ready to TX" status?

No carrier if radio in SSB mode. If the microphone gain is high and there is background noise that will bring up the current and put a signal on the air. With no modulation you will still see power supply current increase on PTT. The power amp will be turned on and you are seeing the idle current plus any background noise modulating the power amp.

P.S. I would say what you are seeing is normal.

It all depends how the linear amplifier/s are biased in the IC7100.

Linear power amplifiers are (usually) biased on at the point that produces maximum linearity and minimum spurii. For a good, high linearity, 12v 100w class power amplifier pallet, the quiescent bias current draw, without any RF output, will be in the range of a few amps. Then you have all the other linear stages prior to the main PA that also draw their own separate bias currents.

The old valve radios like the Kenwood TS520's draw around 60mA of current at 800v, with no RF output. That was 48w worth power consumption before any RF was produced.

Modern radios are about the same, it's just that @ 12v, the current draw is going to be higher.

All Multi-mode HF radios do it. You should worry if the current draw doesn't increase when you hit the PTT button.

His old Yaesu radio would have been the same.

Excellent answers! Thanks specially to Boatanchor for the detailed explanation.

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